Conversion of various feeds to aromatic compounds is an industrially valuable process. Some conventional methods can include conversion of methanol and/or olefins to aromatics in the presence of a molecular sieve, such as ZSM-5. Reactions for conversion of methanol and/or olefins to aromatics can be useful, for example, for creation of aromatics as individual products, or for formation of aromatic and olefin mixtures for use as naphtha boiling range or distillate boiling range fuels.
U.S. Pat. Nos. 4,049,573 and 4,088,706 disclose that methanol can be converted to a hydrocarbon mixture rich in C2-C3 olefins and mononuclear aromatics, particularly p-xylene, by contacting the methanol at a temperature of 250-700° C. and a pressure of 0.2 to 30 atmospheres with a crystalline aluminosilicate zeolite catalyst which has a Constraint Index of 1-12 and which has been modified by the addition of an oxide of boron or magnesium either alone or in combination or in further combination with oxide of phosphorus. The above-identified disclosures are incorporated herein by reference.
Methanol can be converted to gasoline employing the MTG (methanol to gasoline) process. The MTG process is disclosed in the patent art, including, for example, U.S. Pat. Nos. 3,894,103; 3,894,104; 3,894,107; 4,035,430 and 4,058,576. U.S. Pat. No. 3,894,102 discloses the conversion of synthesis gas to gasoline. MTG processes provide a simple means of converting syngas to high-quality gasoline. The ZSM-5 catalyst used is highly selective to gasoline under methanol conversion conditions, and is not known to produce distillate range fuels, because the C10+ olefin precursors of the desired distillate are rapidly converted via hydrogen transfer to heavy polymethylaromatics and C4 to C8 isoparaffins under methanol conversion conditions.
Chinese Patent No. 1,220,288 describes a methanol conversion to aromatics (“MTA”) technology. The MTA technology makes use of modified zeolite catalysts to convert methanol to liquid hydrocarbon products containing aromatics.
Solid oxygen carrier selective hydrogen combustion (“SHC”) catalysts are unique materials where oxygen used to oxidize hydrogen is bound up in the lattice of the catalysts. Due to size exclusion, these materials have been found to be very selective to react with hydrogen alone. For example, U.S. Pat. No. 5,430,210 incorporated herein by reference describes contacting a hydrocarbon and hydrogen stream and an oxygen containing stream with separate surfaces of a metal oxide membrane impervious to non-oxygen containing gases. The metal oxide membrane was selective for hydrogen combustion.
Grasselli et al., Catalytic dehydrogenation (DH) of light paraffins combined with selective hydrogen combustion (SHC), Appl. Catal. A 189 (1999) 1, pp. 1-8, described conversion of propane to propylene that was twice the thermodynamic limit with selectivity to propylene in excess of 90% using Bi2O3 as an SHC catalyst mixed with platinum-based propylene dehydrogenation catalyst. The process operated on intermittent feed cycles of propane and air to regenerate the catalyst. While initial conversion data was promising, the Bi2O3 catalyst was not stable.
Methanol conversion to aromatics is non-selective and exothermic. Insufficient heat removal can lead to run-away temperature excursions that negatively affect aromatic selectivity. There is an ongoing desire to improve methods of converting methanol to aromatics that yield a higher amount of aromatics and are less prone to temperature excursions than prior art methods.